Silicone rubber for polymer insulator has an excellent hydrophobicity with recovery properties, resulting in higher pollution performance. However it is inevitable that even silicone rubber polymer insulators start generating corona discharge with time under humid and polluted conditions. And such a corona discharge causes rubber damage because of acid generation. Since it is assumed that the corona discharge characteristics depend on humidity and polluted conditions, corona discharge tests were conducted on silicone rubber polymer insulators by changing humidity and polluted conditions. As a result, it was verified that the corona discharge phenomena were affected by humidity and pollution even on silicone rubber polymer insulators, and that contribution of corona rings to suppressing the discharge was not large.